Many expected O’Driscoll to captain the tourists in Saturday’s series decider against Australia in Sydney. But he is not skipper as he is not in the team - or even on the replacements' bench.

But Gatland said: “I have never done sentiment. I have to put hand on my heart and say it’s the right rugby decision.

“I would hate to go home thinking we had made calls on trying to avoid criticism or public favour or perception.

“He is obviously very, very disappointed, as any player would be. It’s hard when you’ve been the No.1 in your position for so long - 15 years - and first choice on every team you’ve been a part of.

“There have been a lot of people under him who have experienced the disappointment of Brian O’Driscoll always being selected over them. It’s just part of sport, isn’t it? Sometimes it happens. We’ve made a really tough decision.”

O'Driscoll is on his fourth Lions tour, and scored one of the tourists' greatest ever tries when they last visited Australia 12 years ago.

O’Driscoll’s omission brought a heated reaction from the big names of rugby.

Willie John McBride, the Irishman who holds the record for Lions Tests appearances with 17, even claimed that Gatland was lured into the decision by the enemy.

He said: “I was absolutely gutted. The first thing that came into my mind was that Robbie Deans, the Australian coach, must be laughing all the way.

“The Australian media and others, Eddie Jones the previous Australian coach, have convinced them to drop O’Driscoll which I find amazing.

“He was the guy I’d have tipped as captain of the tour. He’s been a big influence so far. You live and die by the team you pick and we’ll see what Saturday brings.

“O’Driscoll has been the greatest player we’ve ever produced in Ireland and I still think he’s a major influence in any team.”

The British and Irish inquisition: Gatland tries to explain his decision (Image: David Rogers)

Keith Wood, who toured twice with the Lions and has 58 Ireland caps, was equally scathing.

He said: “I’ve been uncomfortable throughout this tour ­whenever Warren Gatland has spoken about the captaincy.

“He tries to de-power it, he consistently says it isn’t about leadership and that isn’t the most important thing.

“Having been on two Lions tours under Martin Johnson, I’d have said the leadership of the captain was the most important thing.

“Brian’s been quiet in the two Tests but at every stage, he’s been the clarion call once Paul O’Connell got injured. I just think Gatland’s made a terrible mistake.”

Former Wales star Jonathan Davies added: “It’s a one-dimensional side on a one-dimensional tour. I’m surprised O’Driscoll isn’t even on the bench.”

Gatland, whose 'day job' is as Wales' head coach, has decided the Lions’ best chance is to name 10 of his Welsh players in the starting XV.

However, Wales have lost six out of six games to Australia in the past 20 months.

Far from going on the defensive, the New Zealander turned his guns on the Wallabies, questioning whether they were able to get themselves “emotionally up” for Saturday having dug so deep to level the series last weekend.

“I’m not sure that they can do that,” said Gatland. “I’ve been involved in teams before and seen how massive emotion can play in terms of results.

“It’s hard to get yourself completely on the edge every week and I think for them that had to be it last week, whereas we think emotionally we can improve.”